Vintage Asylum

you are right -- and AFAIK all the S-7200 does is...

69.130.18.190

mhardy6647

In Reply to: RE: you're not alone posted by avgfan on June 12, 2014 at 13:02:13

...run the A and B (stereo) pairs in parallel if you would switch it to "A+B". This is pretty standard in the solid state arena (even today); of course, paralleling the speakers means that, e.g., two pairs of 4-ohm speakers in parallel produces a 2-ohm (nominal) load on the amp... and many/most amps wouldn't be too happy for two long driving a load of such low impedance.

all the best,
mrh

Follow Ups:

RE: you are right -- and AFAIK all the S-7200 does is... - avgfan 19:16:24 06/12/14 (2)
That's what I was wondering. What did the owners manual say about a 4ohm load on the amp? If I connect 2 pairs of 8 ohm speakers in parallel and run them using the A/B switch, then I'm putting a 4ohm load on the amp, correct? I didn't think that was a good thing to do to your amp.
- RE: you are right -- and AFAIK all the S-7200 does is... - Brian Levy 00:56:37 06/14/14 (1)
  It depends on the amp. The results can vary from not a problem to imploding at any level as the amp is totally unstable.
  
  I do not know about the 7200 but their series of receivers that initially did not have a version with a suffix of "A" and later did were unstable into 4 ohms after the the new FTC rating system was mandated. My son uses a S7650CP with a set of 4 ohm speakers for hours at a time and there are no indications of any problems but, he does not run it hard. My earlier S9500c and SEL200 amp and receiver likewise seem okay with the load but, again, I do not run them hard.
  
  An easy way to tell is to run the unit with an 8 ohms load at your usual listening levels and monitor the heat generated by the power transformer and output transistors. The do the same with a 4 ohm load. If the unit runs appreciably hotter with the 4 ohm load then they do not play nicely together. You can sometimes minimize the issue by reducing the volume and seeing if there heat level reduces.
  
  Another test if you do not the test equipment is to get a pair of the original Advent Loudspeaker, the version with the masonite ringed woofer and a pair of The Smaller Advents Loudspeaker. The closer they come to sounding the same the better the amp is as to handling 4 ohm loads. They were designed to sound the same but with most amps do not as most amps are not as stable with 4 ohm loads. Even with the autoformer McIntosh, they do not sound the same. I did hit nirvana with a Rat Shack STA2250, though. The amp section on this receiver is excellent while the tuner sounds terrible. It is easy to mod to use as a power amp and are usually very inexpensive.
  
  Don Brian Levy, J.D.
  Toronto ON Canada
  - RE: you are right -- and AFAIK all the S-7200 does is... - avgfan 16:42:17 06/16/14 (0)
    Thanks! I went ahead and hooked 'em all up and monitored the heat. There was no appreciable difference that I could tell. I still want a manual though.

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